18uf sub for 20uf in a Fuzz Face?

[jm22]

C2 in a Fuzz Face calls for a 20uf capacitor. I'm looking at a supplier who has some nice looking 18uf capacitors. What would happen if I used an 18uf cap here instead of a 20uf? I see the Tonebender MK1.5 uses a 25uf cap here. What exactly does this capacitor do?

[antonis]

Same thing with what would happen with 22μF, which is absolutely nothing..
(20μF, 50 μF an so are old time values..)

After all, 20% tollerance isn't rare for electros..

[idy]

The 20uf is part of the gain/fuzz control. It bypasses the emitter resistor. The resistor helps set the DC voltage of the transistor, and that cap allows AC (your sound) to see an easier path to ground, lets it swing further.

It is big enough to allow any audio frequency to be treated the same. If you put a much smaller one in, you might have weaker/cleaner bass. Similar circuits use values down to 10uf.

[jm22]

O.k., thanks for the replies.